This invention relates to a method and apparatus for transferring drive.
For many years it has been known to transfer drive by means of direct, permanent mechanical interconnections. An example of such an interconnection occurs when the output shaft of a motor is coupled directly to the member that the motor is intended to drive.
However, in many branches of industry it is commonly required to transfer objects over comparatively large distances and to apply drive at locations remote from eg a motor. It therefore is well known to employ drive-transferring apparatuses such as belts, chains and gear trains in order to achieve these aims.
However, all known drive-transferring technologies are associated with significant disadvantages.
For example, drive belts and drive chains rely on the imparting of tensile forces in order to transfer drive. In drive belts, the use of such forces causes gradual stretching of the belts. Similar effects are observed in drive chains over time.
Prolonged use of belts and chains leads to failure, as a result of friction and wear in the belt/chain members. Failure of a drive belt usually necessitates replacement of the entire belt; or at best a repair that significantly reduces the performance of the belt. Some belt and chain failures are dangerous, especially when fragments of such members are thrown from an apparatus at speed.
It is possible to replace individual links of a drive chain, but this is often a time-consuming process. Hitherto it has not been possible to automate the repair of a broken link in a drive chain.
Gear trains do not suffer from the same disadvantages as belts and chains; however, they are sill prone to wear; they are expensive to manufacture; and they generally require permanent installations including bearings secured to fixed datum points. Also, gear trains generally employ only rigid members and hence they lack some of the versatility inuring to belts and chains, that employ flexible members.
According to the invention in a broad aspect there is provided a drive-transferring apparatus comprising a constraining guide defining a drive-transfer path; and a plurality of drive-transferring members movably captive in the constraining guide; wherein
(i) the constraining guide includes one or more apertures permitting access to one or more of the drive-transferring members; and
(ii) the drive-transferring members are capable of transferring drive between discrete parts of the constraining guide by means of compressive interconnections.
This apparatus overcomes at least some of the disadvantages of the prior art.
In particular, the transferring of drive by compressive interconnection means that tensile failure of components of the apparatus is most unlikely to occur. Furthermore, the use of compressive interconnection means that the drive-transferring members need not be permanently connected together. This in turn means that individual drive-transferring members can readily be repaired or replaced in the apparatus, thereby obviating the difficulties associated with repair of drive belts and drive chains.
The failure modes of apparatuses according to the invention are safer than in the prior art. This is partly because the constraining guide can be designed substantially to enclose all the moveable parts of the device. Thus, component failure may be contained safely within the constraining guide, even when the apparatus is operating at high speed.
Additionally, the use of compressive interconnection means that parts of the apparatus are less likely to be thrown outwardly of the apparatus during failure.
The use of compressive interconnection also means that the drive-transferring elements can be made of materials and shapes inherently resistant to wear and damage yet which also are associated with low frictional forces, thereby improving the efficiency of the apparatus. Particularly suitable shapes for the drive-transferring members are spherical and spheroidal shapes.
All the components of the apparatus of the invention may if desired be manufactured from rigid materials. Thus, it is possible to produce a drive-transferring apparatus that is versatile in terms of the locations between which drive may be transferred; yet which does not suffer from the known disadvantages of flexible drive-transferring members such as belts and chains.
Another possibility is for e.g. the constraining guide to be flexible. This confers versatility on the apparatus of the invention. One preferred form of flexible constraining guide is a hose-like construction that may be formed into a variety of shapes while permitting movement of the drive-transferring members in the manner defined above.
Further, advantageous features of the invention are set out in claims 2-91 appended hereto.
In another broad aspect, the invention is considered to reside in a method of transferring drive comprising imparting motion to one or more of a plurality of drive-transferring members loosely captive in a constraining guide, whereby to cause compressive interconnection of a plurality of said members and thereby transfer drive in the constraining guide.